<!DOCTYPE HTML>
<html>

<head>
    <title>送你一朵玫瑰花</title>
</head>

<body>
    <div id="demo" style="width:96%; height:96%;"><canvas id="c" style="width: 96%;" height="500" width="500"></canvas></div>
    <script>
        // 原文 http://www.romancortes.com/blog/1k-rose/
        // https://blog.csdn.net/u012495579/article/details/71081720 
        var canvas = document.getElementsByTagName('canvas')[0];
        var a = canvas.getContext('2d');
        let { cos, sin, pow, random } = Math;
        c.width = c.height = f = 500; h = -250;
        // 返回 [x,y,z, r,g]
        function p(a, b, c) {
            // 茎
            if (c > 60) {
                return [sin(a * 7) * (13 + 5 / (.2 + pow(b * 4, 4))) - sin(b) * 50, b * f + 50, 625 + cos(a * 7) * (13 + 5 / (.2 + pow(b * 4, 4))) + b * 400, a * 1 - b / 2, a];
            }
            A = a * 2 - 1;
            B = b * 2 - 1;
            if (A * A + B * B < 1) {
                // 叶
                if (c > 37) {
                    n = (j = c & 1) ? 6 : 4; o = .5 / (a + .01) + cos(b * 125) * 3 - a * 300;
                    w = b * h;
                    return [o * cos(n) + w * sin(n) + j * 610 - 390, o * sin(n) - w * cos(n) + 550 - j * 350, 1180 + cos(B + A) * 99 - j * 300, .4 - a * .1 + pow(1 - B * B, -h * 6) * .15 - a * b * .4 + cos(a + b) / 5 + pow(cos((o * (a + 1) + (B > 0 ? w : -w)) / 25), 30) * .1 * (1 - B * B), o / 1e3 + .7 - o * w * 3e-6]
                }
                // 萼片
                if (c > 32) {
                    c = c * 1.16 - .15; o = a * 45 - 20; w = b * b * h; z = o * sin(c) + w * cos(c) + 620;
                    return [o * cos(c) - w * sin(c), 28 + cos(B * .5) * 99 - b * b * b * 60 - z / 2 - h, z, (b * b * .3 + pow((1 - (A * A)), 7) * .15 + .3) * b, b * .7]
                }
                // 花瓣
                o = A * (2 - b) * (80 - c * 2);
                w = 99 - cos(A) * 120 - cos(b) * (-h - c * 4.9) + cos(pow(1 - b, 7)) * 50 + c * 2; z = o * sin(c) + w * cos(c) + 700;
                return [o * cos(c) - w * sin(c), B * 99 - cos(pow(b, 7)) * 50 - c / 3 - z / 1.35 + 450, z, (1 - b / 1.2) * .9 + a * .1, pow((1 - b), 20) / 4 + .05]
            }
        }
        var mp = []; // 深度
        var draw = setInterval(function () {
            for (i = 0; i < 1e4; i++) {
                if (s = p(random(), random(), i % 46 / .74)) { 
                    z = s[2]; 
                    x = ~~(s[0] * f / z - h); 
                    y = ~~(s[1] * f / z - h); 
                    // 深度测试
                    if (!mp[q = y * f + x] | mp[q] > z) {
                        mp[q] = z;
                        let r = ~(s[3] * h);
                        let g = ~(s[4] * h);
                        let b = ~(s[3] * s[3] * -80); // 蓝色几乎没用到
                        a.fillStyle = `rgb(${r},${g},${0})`;
                        a.fillRect(x, y, 1, 1);
                    }
                };
            }
        }, 1);
    </script>
</body>

</html>